The present invention relates to an amphibian and, in particular, to a high speed amphibian with a hull form configured with a single front wheel or track station, and/or for receiving single front wheel or track.
Amphibians for recreation, business, and/or military uses are known. In the past, designers of amphibians have focussed their efforts on optimising either on-water or on-land performance. As a result, either on-water performance has been sacrificed in order to give satisfactory on-land performance, or on-land performance sacrificed to give satisfactory on-water performance. The resulting amphibians are compromised to one degree or another.
To enable an amphibian to attain greater speed on water, it is desirable for the amphibian to be provided with a planing hull. Such a hull can be powered from standing where it is fully displaced to a speed where it can generate sufficient hydrodynamic lift to rise up out of the water and plane across the surface of the water. It is known for such amphibians to have a retractable wheel assembly that enables the wheels of the amphibian to be raised to a retracted position during use of the amphibian on the water. In addition, a hull provides buoyancy to the amphibian such that it floats while in the water.
Generally, for optimal performance, the surface of a planing hull should contain as few discontinuities as possible, as disruptions to the surface of the hull will increase drag and compromise both the hydrodynamic lift achievable and handling on water. However, the nature of an amphibian is such that it can require the surface of the hull to contain discontinuities, such as recesses within which components, for example wheel and suspension assemblies, are located. When attempting to optimise on-water performance, designers of amphibians with retractable wheel and suspension assemblies have expended great effort in providing movable cover mechanisms for wheel arch cut outs to re-establish the smooth uninterrupted lines of a conventional marine hull when the wheels are retracted. Movable covers and plates are known in amphibians for example from U.S. Pat. No. 4,958,584 (Williamson), U.S. Pat. No. 3,421,472 (Oberg), and U.S. Pat. No. 3,280,785 (Oberg). The sliding and/or hinging mechanisms of movable covers or plates are liable to seize up through corrosion, and/or through ingress of mud, sand, silt, salt, or other marine debris. They may also be damaged through collision with objects such as rocks during vehicle mode conversion or off-road use. An amphibian which cannot change mode may be immobilized; either on land, or even worse, on water. Furthermore, the necessity of maintaining and scrupulously cleaning sliding and/or hinging mechanisms may not likely be acceptable to the vehicle owner, who will be accustomed to the less onerous demands of modern cars and boats. Although movable covers or plates have been proposed in several amphibians patents as noted above, these have not made it to series production.
In addressing the above problems in the more recent past, the applicant has retained wheel arches in the hull but developed hydrodynamic aids such as planing plates to help recover at least part of the hull form (as disclosed in the applicant's UK patent no. GB2401832B) and strakes to improve directional stability of the hull when on the plane (as disclosed in the applicant's UK patent no. GB2401833B).
Hulls for amphibians comprising three or more wheels, at least two of which are provided at the front of the amphibian, typically provide sufficient buoyancy on water since the width of the amphibian, and thus the hull, span the width of the front and/or rear axle plus wheels. However, an amphibian having just one front wheel or wheel station presents unique challenges with respect to the hull shape, size, displacement etc., since the amphibian can be required to lean sideways during riding/turning on land, thereby requiring a hull with a relatively narrow width at least at the front, yet the hull must provide sufficient buoyancy to keep the amphibian afloat in the water. Prior art amphibian motorcycles have attempted to meet these challenges using additional movable flotation elements that extend from the hull while the amphibian is in the water. These movable flotation elements may take the form of inflatable bellows, movable or foldable flotation aids, or other forms. Such systems have been bulky, required additional moving parts/components, and can be prone to failure. As such, an amphibian motorcycle with a hull that does not require additional bellows, provides sufficient buoyancy for the amphibian to float in the water, and yet allows the amphibian to adequately lean/turn while on land would be desirable.